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<?php |
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/** |
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* STDIO Server Bridge for MCP Adapter |
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* |
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* This service acts as a bridge between the STDIO protocol and MCP servers, |
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* allowing any registered server to be exposed via command-line interface. |
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* |
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* @package McpAdapter |
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*/ |
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|
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declare( strict_types=1 ); |
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|
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namespace WP\MCP\Cli; |
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|
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use WP\MCP\Core\McpServer; |
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use WP\MCP\Infrastructure\ErrorHandling\McpErrorFactory; |
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use WP\MCP\Transport\Infrastructure\JsonRpcResponseBuilder; |
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use WP\MCP\Transport\Infrastructure\RequestRouter; |
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|
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/** |
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* STDIO Server Bridge - Exposes MCP servers via STDIO protocol |
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* |
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* This service handles JSON-RPC communication over stdin/stdout and delegates |
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* requests to the appropriate MCP server. Unlike transport implementations, |
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* this is a presentation layer service that can work with any server. |
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*/ |
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class StdioServerBridge { |
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|
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/** |
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* The MCP server to expose via STDIO. |
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* |
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* @var \WP\MCP\Core\McpServer |
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*/ |
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private McpServer $server; |
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|
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/** |
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* Request router for handling MCP requests. |
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* |
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* @var \WP\MCP\Transport\Infrastructure\RequestRouter |
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*/ |
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private RequestRouter $request_router; |
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|
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/** |
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* Whether the bridge is currently running. |
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* |
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* @var bool |
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*/ |
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private bool $is_running = false; |
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|
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/** |
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* Initialize the STDIO server bridge. |
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* |
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* @param \WP\MCP\Core\McpServer $server The MCP server to expose. |
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*/ |
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public function __construct( McpServer $server ) { |
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$this->server = $server; |
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|
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// Create request router using server's infrastructure |
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$this->request_router = $this->create_request_router(); |
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} |
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|
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/** |
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* Create a request router for the server. |
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* |
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* @return \WP\MCP\Transport\Infrastructure\RequestRouter |
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*/ |
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private function create_request_router(): RequestRouter { |
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// Create transport context using server's infrastructure |
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$context = $this->server->create_transport_context(); |
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|
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return $context->request_router; |
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} |
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|
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/** |
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* Start the STDIO server bridge. |
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* |
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* This method reads JSON-RPC messages from stdin and writes responses to stdout. |
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* It runs in a loop until terminated or until it receives a shutdown signal. |
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* |
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* @throws \RuntimeException If STDIO transport is disabled. |
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*/ |
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public function serve(): void { |
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/** |
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* Filters whether the STDIO transport is enabled. |
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* |
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* Return false to disable STDIO transport entirely. This prevents |
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* the WP-CLI `mcp-adapter serve` command from functioning. |
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* |
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* @since 0.3.0 |
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* |
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* @param bool $enabled Whether STDIO transport is enabled. Default true. |
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*/ |
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$enable_serve = apply_filters( 'mcp_adapter_enable_stdio_transport', true ); |
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|
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if ( ! $enable_serve ) { |
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throw new \RuntimeException( |
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'The STDIO transport is disabled. Enable it by setting the "mcp_adapter_enable_stdio_transport" filter to true.' |
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); |
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} |
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|
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$this->is_running = true; |
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|
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// Log to stderr to keep stdout clean for MCP messages |
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$this->log_to_stderr( sprintf( 'MCP STDIO Bridge started for server: %s', $this->server->get_server_id() ) ); |
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|
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// Main server loop |
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while ( $this->is_running ) { |
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try { |
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// Read a line from stdin (blocking) |
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$input = fgets( STDIN ); |
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|
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if ( false === $input ) { |
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// EOF or error reading from stdin |
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break; |
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} |
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|
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// Trim newline delimiter |
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$input = rtrim( $input, "\r\n" ); |
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|
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if ( empty( $input ) ) { |
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// Empty line, continue reading |
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continue; |
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} |
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|
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// Process the request and get response |
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$response = $this->handle_request( $input ); |
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|
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// Write response to stdout with newline delimiter |
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if ( ! empty( $response ) ) { |
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// Use fwrite() for precise binary-safe JSON-RPC protocol communication. |
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// WP_CLI output functions would add formatting/prefixes that break MCP protocol. |
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// MCP requires exact control over stdout for machine-to-machine communication. |
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fwrite( STDOUT, $response . "\n" ); // phpcs:ignore |
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fflush( STDOUT ); |
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} |
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} catch ( \Throwable $e ) { |
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// Log errors to stderr |
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$this->log_to_stderr( 'Error processing request: ' . $e->getMessage() ); |
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|
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$error_response = $this->encode_response( |
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JsonRpcResponseBuilder::create_error_response( |
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null, |
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array( |
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'code' => McpErrorFactory::INTERNAL_ERROR, |
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'message' => 'Internal error', |
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'data' => array( |
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'details' => $e->getMessage(), |
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), |
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) |
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) |
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); |
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|
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fwrite( STDOUT, $error_response . "\n" ); // phpcs:ignore |
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fflush( STDOUT ); |
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} |
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} |
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|
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$this->log_to_stderr( 'MCP STDIO Bridge stopped' ); |
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} |
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|
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/** |
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* Log a message to stderr. |
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* |
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* @param string $message The message to log. |
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*/ |
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private function log_to_stderr( string $message ): void { |
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fwrite( STDERR, "[MCP STDIO Bridge] $message\n" ); // phpcs:ignore |
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} |
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|
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/** |
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* Handle a JSON-RPC request string and return a JSON-RPC response string. |
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* |
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* @param string $json_input The JSON-RPC request string. |
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* |
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* @return string The JSON-RPC response string (empty for notifications). |
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*/ |
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private function handle_request( string $json_input ): string { |
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try { |
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// Parse JSON-RPC request |
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$request = json_decode( $json_input, true ); |
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|
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if ( json_last_error() !== JSON_ERROR_NONE ) { |
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return $this->create_error_response( |
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null, |
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McpErrorFactory::PARSE_ERROR, |
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'Parse error', |
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'Invalid JSON was received by the server.' |
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); |
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} |
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|
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// Validate JSON-RPC structure |
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if ( ! is_array( $request ) ) { |
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return $this->create_error_response( |
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null, |
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McpErrorFactory::INVALID_REQUEST, |
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'Invalid Request', |
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'The JSON sent is not a valid Request object.' |
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); |
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} |
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|
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// Check for JSON-RPC version |
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if ( ! isset( $request['jsonrpc'] ) || '2.0' !== $request['jsonrpc'] ) { |
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return $this->create_error_response( |
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$request['id'] ?? null, |
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McpErrorFactory::INVALID_REQUEST, |
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'Invalid Request', |
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'The JSON-RPC version must be 2.0.' |
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); |
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} |
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|
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// Extract request components |
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$method = $request['method'] ?? null; |
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$params = $request['params'] ?? array(); |
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$id = $request['id'] ?? null; |
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|
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if ( ! is_string( $method ) ) { |
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return $this->create_error_response( |
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$id, |
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McpErrorFactory::INVALID_REQUEST, |
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'Invalid Request', |
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'Method must be a string.' |
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); |
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} |
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|
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// Convert params to array if it's an object |
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if ( is_object( $params ) ) { |
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$params = (array) $params; |
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} |
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|
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if ( ! is_array( $params ) ) { |
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$params = array(); |
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} |
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|
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// Route the request to the appropriate handler |
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$result = $this->request_router->route_request( |
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$method, |
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$params, |
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$id, |
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'stdio' |
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); |
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|
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// If this is a notification (no id), don't send a response |
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if ( null === $id ) { |
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return ''; |
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} |
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|
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// Format the response |
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return $this->format_response( $result, $id ); |
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} catch ( \Throwable $e ) { |
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// Handle unexpected errors |
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return $this->create_error_response( |
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null, |
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McpErrorFactory::INTERNAL_ERROR, |
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'Internal error', |
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$e->getMessage() |
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); |
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} |
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} |
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|
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/** |
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* Create a JSON-RPC error response. |
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* |
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* @param mixed $id The request ID (can be null). |
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* @param int $code The error code. |
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* @param string $message The error message. |
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* @param string $data Optional error data. |
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* |
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* @return string The JSON error response string. |
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*/ |
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private function create_error_response( $id, int $code, string $message, string $data = '' ): string { |
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$error = array( |
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'code' => $code, |
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'message' => $message, |
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); |
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|
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if ( '' !== $data ) { |
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$error['data'] = $data; |
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} |
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|
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return $this->encode_response( JsonRpcResponseBuilder::create_error_response( $id, $error ) ); |
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} |
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|
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/** |
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* Encode a JSON-RPC response to a string. |
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* |
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* @param array $response JSON-RPC response structure. |
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* |
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* @return string JSON-encoded response string. |
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*/ |
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private function encode_response( array $response ): string { |
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$json = wp_json_encode( $response, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE ); |
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|
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if ( false === $json ) { |
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// Fallback when JSON encoding fails - use constant for consistency. |
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return sprintf( |
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'{"jsonrpc":"2.0","error":{"code":%d,"message":"Internal error"},"id":null}', |
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McpErrorFactory::INTERNAL_ERROR |
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); |
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} |
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|
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return $json; |
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} |
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|
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/** |
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* Format a handler result as a JSON-RPC response. |
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* |
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* @param array $result The handler result. |
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* @param mixed $id The request ID. |
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* |
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* @return string The JSON-RPC response string. |
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*/ |
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private function format_response( array $result, $id ): string { |
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// Check if result contains an error |
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if ( isset( $result['error'] ) ) { |
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$error = $result['error']; |
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|
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// Ensure error has required fields |
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$error_payload = array( |
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'code' => $error['code'] ?? McpErrorFactory::INTERNAL_ERROR, |
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'message' => $error['message'] ?? 'Internal error', |
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); |
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|
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// Add data field if present |
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if ( isset( $error['data'] ) ) { |
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$error_payload['data'] = $error['data']; |
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} |
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|
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return $this->encode_response( JsonRpcResponseBuilder::create_error_response( $id, $error_payload ) ); |
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} |
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|
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return $this->encode_response( JsonRpcResponseBuilder::create_success_response( $id, $result ) ); |
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} |
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|
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/** |
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* Stop the STDIO server bridge. |
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*/ |
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public function stop(): void { |
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$this->is_running = false; |
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} |
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|
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/** |
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* Get the server this bridge is exposing. |
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* |
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* @return \WP\MCP\Core\McpServer |
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*/ |
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public function get_server(): McpServer { |
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return $this->server; |
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} |
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} |
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|
